Hi, Pete - I must admit I'm having difficulty understanding your issue, and I've been using the PFC since it debuted. Could you maybe include a picture of the window in question?
Since you've established that you're using the PFC and DataWindow Controls inherited from the PFC's base DW, u_dw, the object inheritance chain really doesn't matter. What is important is the quantity and purpose of the DW's in the window, are they logically connected (do they utilize the PFC's linkage service, for example?) and what has the user or code done in order to cause the ItemChanged event in one of these windows to be executed?
Then if you could please rephrase your question in less abstract terms? For example: "I have a sheet window that lists widget orders, a list of the whatzits contained in the currently selected widget order, and a list of the whoozits that are responsible for the currently selected whatzit. The user changes some info in the window (in a whatzit or a whoozit), causing the ItemChanged event in the Widget List DW to fire. How do I tell if the user changed a whatzit or a whoozit? I need to know this because (explain...)"
Much easier for us to visualize and therefore, to better advise you. It will also help if you could give us some idea of your level of expertise with PB and with using the PFC.